Additional CSS field is no longer full-height in Site Editor

[metabreakr]

Quick summary

In previous versions of Gutenberg, the Additional CSS field, found in the Site Editor, was the full height of the sidebar. Presently, it is rather small and needs to be manually resized to view CSS, as shown here:

2025-01-03_11-26-59.mp4

Steps to reproduce

1. Activate a FSE theme, such as TT5
2. Visit the Site Editor
3. In Global Styles, go to Additional CSS
4. Observe that the input field is small

What you expected to happen

I expected the Additional CSS field to be full-height, as in previous iterations.

What actually happened

The Additional CSS field was not full-height.

Impact

All

Available workarounds?

Yes, easy to implement

If the above answer is "Yes...", outline the workaround.

It is possible to manually resize the field, however this must be done each time the Site Editor is revisited.

Platform (Simple and/or Atomic)

No response

Logs or notes

First noted here: p1728644178405839-slack-CBTN58FTJ

[github-actions]

OpenAI suggested the following labels for this issue:

• [Feature Group] Appearance & Themes: The issue relates to the design aspect of the Site Editor and how CSS fields are displayed.
• [Feature] Full Site Editor: The problem specifically involves the Full Site Editor where the Additional CSS field is located.
• [Feature] Global Styles: The issue highlights a functionality within the Global Styles section, particularly affecting the CSS field.

[annezazu]

This is related to Core and needs to be reported in Gutenberg.

[metabreakr]

@annezazu Will someone triage and post there, or should I do that myself?

[annezazu]

Handled it: WordPress/gutenberg#68928